Optical fiber sensor having electrical connectors

ABSTRACT

An optical fiber sensor has a sensor band of optical sensor fibers. The band is connected on both ends to a transmitter unit and a receiver unit, the transmitter unit feeding optical signals into the optical fibers, the signals being optically evaluated with regard to the intensity thereof by the receiver unit. Parallel electrical conductors are located in the sensor band and can, for example, be designed as ribbon cables. The electrical conductors allow an additional electrical connection of the transmitter unit and the receiver unit, so that external cables advantageously need only be connected to one of the two units. The difficulty of connection is thereby reduced, and the wearing comfort is increased for the application of the fiber sensor, for example, as a back sensor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to PCT Application No. PCT/EP2008/059254 filed on Jul. 15, 2008, DE Application No. 10 2007 046 385.7 filed on Sep. 21, 2007 and DE Application No. 10 2007 034 264.2 filed on Jul. 18, 2007, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

An optical fiber sensor may have at least one optical sensor fiber which is equipped at its ends with an optical transmitter unit for feeding in a measurement signal, and with an optical receiver unit for registering this measurement signal, wherein the transmitter unit and the receiver unit also have electrical connections. The transmitter unit and receiver unit are physically separated from one another, that is to say they are each autonomous units.

By way of example, a fiber sensor of the type mentioned initially is described in U.S. Pat. No. 6,940,062 B2. This optical fiber sensor may, for example, be used to determine deformation, when the optical fiber sensor is applied in such a manner that the deformation of a component to which the optical fiber sensor is fitted causes bending of the optical sensor fiber of the optical fiber sensor. This can be verified by the influence of the bending on the optical attenuation behavior of the sensor fiber. For this purpose, a measurement signal is fed into the optical sensor fiber from an optical transmitter unit, and the measurement signal is evaluated by a receiver unit at the other end of the optical sensor fiber. The light intensity of the received measurement signal can be used to deduce the bending state of the sensor fiber. The optical transmitter unit and the optical receiver unit can each be supplied with power and the measurement variable can be read electrically, via plug contacts.

However, the design of the fiber sensor according to U.S. Pat. No. 6,940,062 B2 may cause problems in certain applications. For example, according to EP 968 400 B1, an application for an optical fiber sensor is described in which the movements of the human body are intended to be monitored. For this purpose, the optical fiber sensor is attached to the human body. In this case, however, electrical connections and the connecting lines fitted at both ends of the sensor fiber restrict the freedom of movement of the subject, thus limiting the validity of the measurement results that are determined.

EP 968 400 B1 therefore proposes that the transmitter unit and the receiver unit be combined in one housing. This results in the capability to provide the optical fiber sensor with the electrical contact at only one end. In order to allow the transmitter unit and the receiver unit to be joined together, the optical fiber sensors are laid in loops in the sensor ribbon, such that the start and the end of the respective sensor fiber are located at one end of the sensor ribbon. In this case, it is assumed that this measure results in the cross section of the sensor ribbon itself being twice as great than would be the case if the sensor fiber were to extend from one end of the sensor ribbon to the other end of the sensor ribbon. This is because the loss of wearing comfort associated with this outweighs the cumbersome contact being made at both ends.

SUMMARY

One potential object is to specify an optical fiber sensor whose wearing comfort and operating comfort are comparatively high.

The inventors propose a fiber sensor specified initially, in that at least one electrical line is routed in the fiber sensor, parallel to the optical sensor fiber and connects at least some of the electrical connections of the receiver unit to at least some of the connections of the transmitter unit. For the purposes of the device proposed here, an electrical line should in general be understood to be an arrangement for carrying electrical signals or supply currents. In this case, the electrical line may have one or more cores, that is to say that a plurality of electrical signals and supply currents are transported in one line. The provision of the electrical line running parallel to the sensor fiber means that it is possible on the one hand to dispense with all the optical sensor fibers being fed back to a single housing, and with units which are physically independent of one another being used for transmission and reception of the measurement signals (transmitter unit and receiver unit) at both ends of the sensor fiber. However, complex contact with the two units can be simplified by laying one electrical line between the transmitter unit and the receiver unit, by which contacts which are intended for the one unit can be laid to contacts of the other unit.

In this case, it is particularly advantageous for the transmitter unit or the receiver unit to have exclusively electrical connections, which are connected via the electrical line. At least one of the units is therefore advantageously completely free of external electrical connections, which means that this unit need not make contact with any external electrical connecting lines. In fact, all the electrical contact lines which are required for operation of the relevant unit run via the electrical line which runs parallel to the optical sensor fiber. This considerably improves the wearing comfort, because an electrical contact is required with only one of the units (transmitter unit or receiver unit). Furthermore, the wearing comfort of the sensor fiber, which, for example, may be integrated in a sensor ribbon, is also only insignificantly adversely affected by the additional presence of a further electrical line. This electrical line may have signal lines for a plurality of optical sensor fibers, since the cross section which is required for this purpose is less than that required for the optical sensor lines.

One advantageous refinement is obtained if the transmitter unit and the receiver unit have exclusively electrical connections which are connected via the electrical line. This refinement depends on the optical fiber sensor operating autonomously. This means that the fiber sensor must on the one hand have a power source for operation, while on the other hand a wireless interface must be available for reading the measurement data, or it must have a memory for this data in order that this data can be evaluated once the measurement has been completed. In this case, an electrical contact which advantageously need not be connected during the measurement can be provided for reading purposes. In the case of an autonomously operating optical fiber sensor, the laying of an electrical line parallel to the optical sensor fiber has the advantage that the components which are required for autonomous operation of the fiber sensor need be provided only once in each case. For example, the transmitter unit can conceal the electrical voltage source, and the receiver unit can also be supplied electrically via the electrical line. If the memory module for the measured values and a wireless interface for transmitting them are also intended to be provided in the transmitter unit (for example in order to keep the receiver unit as small as possible), signal lines would also have to be laid between the receiver unit and the transmitter unit.

One development of the idea provides for the at least one optical sensor fiber to be integrated, in particular embedded, in a sensor ribbon. Embedding in a sensor ribbon advantageously allows simple handling of the optical fiber sensor. On the one hand, the sensor ribbon provides a certain amount of protection for the sensitive optical sensor fibers. On the other hand, a plurality of sensor fibers can be combined in a defined position with respect to one another in the sensor ribbon.

When using a sensor ribbon, it is advantageous for the electrical line to be in the form of a line conductor, and likewise to be integrated, in particular embedded, in the sensor ribbon. The sensor ribbon can then advantageously be laid easily, in order to carry out a measurement in the desired application. In this case, there is no need to pay particular attention to the optical or electrical sections. In this case, it is particularly advantageous for the electrical line to have essentially the same diameter as the at least one optical fiber. From the manufacturing point of view, this allows this to be laid easily together with the optical sensor fibers or the optical sensor fiber, and combined to form a sensor ribbon. The complete sensor ribbon may then in particular have a standard physical height which, in the area of the electrical line, also corresponds to the physical height of the area in which there are preferably a plurality of sensor fibers.

Another advantageous option is for the electrical line to be in the form of a ribbon conductor. A ribbon conductor advantageously has a very small physical height, thus allowing it to be routed easily parallel to the sensor fiber without significantly increasing the physical space occupied by the sensor ribbon. In this case, it is particularly advantageous for the ribbon conductor and the sensor ribbon to be arranged side-by-side. This means that the ribbons are each located with the broad face of the ribbon adjacent to one another, that is to say, not edge-to-edge, but rather one above the other. The large joint surface area which is available thereby advantageously allows a fixed assembly to be produced. At the same time the ribbon conductor can in this case mechanically support the sensor fibers. The ribbon conductor and the sensor ribbon for example may be connected to one another by an adhesive layer. From the manufacturing point of view, this can be carried out particularly easily, in particular for small batches. The adhesive layer may be applied to one of the ribbons. However, it is also possible to use a double-sided adhesive tape.

An alternative option is for the electrical line to be in the form of a ribbon conductor, by conductive paths being produced directly on the sensor ribbon. In this case, it is possible to use the normal methods for manufacturing electrical conductive paths. By way of example, photomechanical methods may be used, in which, after suitable structuring of the ribbon surface, the conductive paths are produced by etching. Another option is to produce the conductive paths on the sensor ribbon by coating, using templates. In any case, a particularly space-saving solution is achieved by direct production of the conductive paths on the sensor ribbon.

It is also advantageous for the assembly comprising the sensor ribbon and the ribbon conductor to be sheathed with a sheath. This sheath provides additional protection for the entire assembly, and in particular when the conductive paths are produced directly on the sensor ribbon, the sheath additionally provides electrical insulation, which advantageously extends the options for use of the fiber sensor that is produced.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 shows one exemplary embodiment of the proposed optical fiber sensor, schematically in the form of a longitudinal section,

FIG. 2 shows a plan view of one exemplary embodiment of the proposed fiber sensor, which is mounted on a carrier ribbon, and

FIGS. 3 to 5 show cross sections through the sensor ribbons for different exemplary embodiments of the fiber sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

An optical fiber sensor 11 as shown in FIG. 1 comprises three units: an optical transmitter unit 12, a sensor ribbon 13 and an optical receiver unit 14. The sensor unit 12 is fitted to one end of the sensor ribbon, and the receiver unit 14, which is physically separated from the transmitter unit, is fitted to the other end of the sensor ribbon 13.

The sensor ribbon has a plurality of optical sensor fibers 15 which each have sections 16 that are sensitive to bending, at different points on the sensor ribbon. This allows bending of the sensor ribbon 13 to be determined with position resolution. Furthermore, an electrical line which is in the form of a line conductor 17 runs parallel to the sensor fibers. Optical contact is made with the sensor fibers 15 in the receiver unit 14 and in the transmitter unit 12 via optical interfaces 18. Furthermore, the transmitter unit 12 and the receiver unit 14 have electrical connections 19 e and 19 s, via which contact can be made with the line conductor. These are illustrated only schematically in FIG. 1. If the line conductor has a plurality of cores, then a plurality of connections 19 e, 19 s are, of course, also necessary, although these have been omitted in FIG. 1, for the sake of better clarity.

In the case of the solution for the optical fiber sensor as shown in FIG. 1, this represents an autonomous system. The transmitter unit 12 and the receiver unit 13 each comprise printed circuit boards 20 on which a protective cap 21 is provided. The protective cap acts as a housing for the respective driver electronics, a voltage supply and a radio module for passing on the measured values without the use of cables, and for reception of control signals for the optical fiber sensor. However, these components are not illustrated in any more detail.

The fiber sensor illustrated in FIG. 2 has the following differences in comparison to FIG. 1. In contrast to the sensor ribbon 13 shown in FIG. 1, in the case of the sensor ribbon 13 shown in FIG. 2, the electrical conductor (in the form of a line conductor and not illustrated) is also embedded in the sensor ribbon 13. According to FIG. 1, the line conductor 17 runs parallel alongside the sensor ribbon 13. The transmitter unit 12 and the receiver unit 14 are also each completely integrated in a housing. Furthermore, the transmitter unit 12 additionally has electrical connections, which are not illustrated in any more detail but which can make contact with a plug 22. This allows a supply and signal line 23 to be connected to the transmitter unit 12. The electrical supply to the receiver unit 14 and the transmission of signals between the transmitter unit 12 and the receiver unit 14 take place via the line conductor which is not illustrated (cf., analogously, 17 in FIG. 1), which means that there is no need for any external contact with the receiver unit 14.

Since the receiver unit 14 has no external contacts, the optical fiber sensor as shown in FIG. 2 can be mounted on a carrier ribbon 24. This comprises a flexible substrate 25 which, for example, can be firmly adhesively bonded to the skin of a subject when the fiber sensor is used as a back sensor. An adhesive which is compatible with skin is used in this case. The flexibility of the substrate ensures a high level of wearing comfort, since the carrier ribbon can follow the movements of the spinal column and the elastic changes to the skin associated with this. An elastic cover layer 26 is also applied to the substrate 25 so as to create a pocket which is open on one side. The fiber sensor can be pushed into this pocket, with its contour 27 being visible under the elastic cover layer. In this case, the receiver unit 14 is located at the end of the pocket. The transmitter unit 12 is mounted on a rigid fixing plate 28, thus providing a reference point on the carrier ribbon 24 for the fiber sensor.

FIG. 3 shows a cross section through the sensor ribbon 13, as could be used by way of example for the fiber sensor shown in FIG. 2. The line conductors 17, two of which are provided, are arranged on the two edges 29 and therefore enclose the sensor fiber 15 between them. This has the advantage that the sensor fibers 15, which are more sensitive than the line conductors 17, are protected. The line conductors 17 and the sensor fibers 15 are jointly embedded in the material of the sensor ribbon 13, and this can be done, for example, by encapsulation in a silicone rubber, which ensures a high degree of flexibility of the resultant sensor ribbon 13.

FIG. 4 shows another possible form of the sensor ribbon 13. This has exclusively sensor fibers 15 which can be encapsulated in the manner described in relation to FIG. 3. Furthermore, an adhesive layer 30 is applied to the lower face of the sensor ribbon 13, and connects the sensor ribbon 13 to an electrical ribbon conductor 31. The ribbon conductor 31 has a substrate 32 on which conductive paths 33 have been produced, for example by structuring by etching. The entire assembly comprising the sensor ribbon 13 and the ribbon conductor 31 is additionally provided with an elastic sheath 34, for example composed of rubber.

As shown in FIG. 5, the conductive paths 33 are produced directly on the sensor ribbon 13. This can be done, for example, by coating using the CVD method. The functionality of the ribbon conductor 33 as shown in FIG. 4 is therefore at the same time integrated in the sensor ribbon 13. This assembly is also provided with a sheath 34, corresponding to the embodiment shown in FIG. 4.

The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004). 

1-11. (canceled)
 12. An optical fiber sensor comprising: an optical sensor fiber having first and second ends; an optical transmitter unit provided at the first end of the optical sensor fiber to transmit a measurement signal to the optical sensor fiber, the transmitter unit having an electrical connection; an optical receiver unit physically separated from the transmitter unit and provided at the second end of the optical sensor fiber to receive the measurement signal, the receiver unit having an electrical connection; and an electrical line routed in the fiber sensor, parallel to the optical sensor fiber to connect the electrical connection of the receiver unit to the electrical connection of the transmitter unit.
 13. The fiber sensor as claimed in claim 12, wherein at least one of the transmitter unit and the receiver unit have a plurality of electric connections, and the transmitter unit or the receiver unit has all electrical connections connected via the electrical line.
 14. The fiber sensor as claimed in claim 13, wherein the transmitter unit and the receiver unit each have a plurality of electrical connections, and all electrical connections of the transmitter unit and receiver unit are connected via the electrical line.
 15. The fiber sensor as claimed in claim 12, wherein the optical sensor fiber is integrated in a sensor ribbon.
 16. The fiber sensor as claimed in claim 15, wherein the electrical line is a line conductor, and is likewise integrated in the sensor ribbon.
 17. The fiber sensor as claimed in claim 16, wherein the electrical line has substantially the same diameter as the optical fiber.
 18. The fiber sensor as claimed in claim 15, wherein the electrical line is in the form of a ribbon conductor.
 19. The fiber sensor as claimed in claim 18, wherein the ribbon conductor and the sensor ribbon are arranged side-by-side.
 20. The fiber sensor as claimed in claim 19, wherein the ribbon conductor and the sensor ribbon are connected to one another by an adhesive layer.
 21. The fiber sensor as claimed in claim 18, wherein the electrical line is in the form of conductive paths produced directly on the sensor ribbon.
 22. The fiber sensor as claimed in claim 18, wherein the sensor ribbon and the ribbon conductor together form an assembly, and the assembly is sheathed with a sheath.
 23. A wearable optical fiber sensor comprising: a sensor ribbon having a plurality of optical sensor fibers, the sensor ribbon having first and second ends; an optical transmitter unit provided at the first end of the optical sensor ribbon to transmit respective measurement signals to the optical sensor fibers, the transmitter unit having an electrical connection; an optical receiver unit physically separated from the transmitter unit and provided at the second end of the optical sensor ribbon to receive respective measurement signals from optical sensor fibers, the receiver unit having an electrical connection; an electrical line embedded in the sensor ribbon, parallel to the optical sensor fibers to connect the electrical connection of the receiver unit to the electrical connection of the transmitter unit; and a battery power supply provided at the transmitter unit or the receiver unit.
 24. The wearable optical fiber sensor according to claim 23, further comprising a wireless transmitter to transmit an output signal to an external receiver, the output signal corresponding to the measurement signals.
 25. The wearable optical fiber sensor according to claim 23, further comprising a memory to store an output signal corresponding to the measurement signals. 